Radio frequency occupancy sensing load control

ABSTRACT

An occupancy sensing load control system is disclosed. The occupancy sensing load control system includes a detector unit, an occupancy/vacancy signal generator and a load control circuit. The detector unit detects RF signals emitted by cell phones or similar mobile communication devices within an area being monitored. The occupancy/vacancy signal generator generates a control signal for the load control circuit based on the detection of a qualified RF signal or the absence of such signal within a predetermined time interval. The occupancy sensing load control system may also include a signal-generating unit for generating a pseudo base station signal based on zone information of neighboring base stations for transmission to a mobile phone in the detection area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/556,212, filed Nov. 30, 2014, now allowed. This application alsoclaims priority from U.S. provisional application Ser. No. 61/913,285filed on Dec. 7, 2013, incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

NOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION

A portion of the material in this patent document is subject tocopyright protection under the copyright laws of the United States andof other countries. The owner of the copyright rights has no objectionto the facsimile reproduction by anyone of the patent document or thepatent disclosure, as it appears in the United States Patent andTrademark Office publicly available file or records, but otherwisereserves all copyright rights whatsoever. The copyright owner does nothereby waive any of its rights to have this patent document maintainedin secrecy, including without limitation its rights pursuant to 37C.F.R. §1.14.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electric load control systems employingoccupancy or vacancy sensors for detecting an occupancy or a vacancy ina space, and more particularly, to a load control system including aradio frequency detector for detecting an occupancy or a vacancy in aspace and a load control device for controlling the amount of powerdelivered to an electrical load in response to the detection ofoccupancy or vacancy.

2. Description of Background Art

Energy efficiency measures in buildings often utilize automated controlsystems that detect occupancy and/or vacancy conditions in a space anduse such information to control electrical load devices, such as, forexample, lighting fixtures, heating units, air conditioning units,ventilation units, or security systems.

Conventionally, load control systems employ occupancy sensors thatdetect motion within a space in order to determine the occupancy orvacancy condition. Some of the most common motion detection sensorsinclude passive infrared (“PIR”) sensors, ultrasonic sensors and acombination of the two.

Such types of occupancy sensors, however, can only detect moving objectsand usually require a direct line of sight between the sensor and theobject. In the absence of occupant movements, the occupancy may remainundetected thus resulting in false triggering of the vacancy condition.Various objects within the space, room partitions or unusual roomconfigurations can partially block the view of sensors and also causefalse triggering. Improper sensor installation or changes in the roominterior may also be a source of erroneous operation of the loadcontrol. When conventional occupancy sensors are used to switch lightson and off in a room, false triggering, inadequate sensor spacing, orview-blocking objects may cause a commonly observed condition whenoccupants are left in the dark.

The failures of occupancy sensors to detect vacancy condition oftencause occupants' complaints, create work inefficiencies and mayjeopardize occupant safety. All this slows the adoption of energy savingmeasures which rely on electric load control based on space occupancy.

It is therefore an object of this invention to provide an improved loadcontrol system which does not require the direct line of sight or objectmotion for occupancy or vacancy detection. It is another object of thisinvention to provide an independent method of detecting occupancy and/orvacancy in a space which can be used for improving the detection rate.The occupancy sensing load control system of this invention can be canbe used in a stand-alone operation or can be integrated with other typesof occupancy/vacancy sensing devices. Other objects and advantages ofthis invention will be apparent to those skilled in the art from thefollowing disclosure.

BRIEF SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to radio frequencyoccupancy sensing load control systems which may be employed to controlelectric load within a certain area. More particularly, this inventionis directed to a system for detecting the presence or absence of amobile radio frequency communication device in such area.

According to one aspect of the invention, the occupancy sensing loadcontrol system uses radio frequency (RF) signals emitted by electricallypowered mobile radio-emitting devices such as hand held cell phones orsimilar personal wearable communication devices which are energized byan internal or external battery and which can be reasonably associatedwith people who carry such devices with them in and out from a space.

According to one aspect of the invention, the occupancy sensing loadcontrol system can be made responsive to radio frequency (RF) signalsemitted by mobile communication devices associated with vehicles such ascell phones, radios or global positioning systems used for mobile fleetcommunication.

In at least one embodiment, the invention features an occupancy detectorload control system comprising a radio-frequency detector configured todetect the presence or absence of a personal radio-emittingcommunication device within a predetermined distance from the sensor anda load control device connected between an electrical power source andan electrical load. The control device is configured to receive signalsfrom the detector and control the current supplied to the electricalload in a predetermined dependence on the detection of the presence orabsence of the radio-emitting device.

The load control system may be amenable to include the detection of abroad range of mobile communication devices, including mobile phones,cellular phones, satellite phones, smart phones, pagers, personaldigital assistants (PDA), tablet computers, mobile personal computers,wireless medical devices, wireless network devices, personal areanetwork devices, wireless headsets, portable radios, cordlesstelephones, and global positioning systems (GPS).

In various implementation of the detector, it may be configured foroccupancy/vacancy detection within a predefined area and may furtherinclude means for adjusting the detection range. According to a furtherimplementation, the operational radio frequencies of the detector caninclude the range from 50 MHz to 6 GHz. According to a yet furtherimplementation, the operational radio frequencies of the detector caninclude at least one of the following ranges: 824-849 MHz and 1850-1910MHz.

In at least some embodiments, the load control system may be configuredto produce various predefined control signals. The system mayparticularly comprise a signal-generating unit for generating a radiosignal that can trigger a response signal from the radio-emittingdevice. The system may also be configured to produce an audible orvisual alarm.

According to one embodiment, the load control system may be configuredto control the amount of power delivered from an electrical power sourceto an electrical load provided in a space and may comprise: asignal-generating unit for generating a pseudo base station signal basedon zone information of neighboring base stations for transmission to amobile phone in a detection area; a detecting unit adapted to detect aresponse signal that a mobile phone transmits in response to the pseudobase station signal; and a control unit that controls the operation ofthe load in response to the detection of the response signal by thedetecting unit.

In at least one embodiment, a method of controlling the amount of powerdelivered from an electrical power source to an electrical load within aspace is provided. Such method may comprising the steps of providing aradio-frequency sensor in such space; detecting a vacancy condition bythe sensor in response to the absence of one or more predeterminedradio-frequency signals during a predetermined period of time;generating a vacant control signal by the sensor in response to the stepof detecting the vacancy condition; and ceasing the delivery of power tothe electrical load in response to the step of generating the vacantcontrol signal from the sensor.

In at least one embodiment, the method of controlling the amount ofpower delivered from an electrical power source to an electrical loadmay comprise the steps of (a) transmitting a pseudo base station signalwithin a detection area, using zone information of neighboring basestations to generate said pseudo base station signal; b) detecting avacancy condition in the detection area in response to the absence of apredetermined response signal to the pseudo base station signal; and (c)ceasing the delivery of power to the electrical load in response to thestep of detecting the vacancy condition in the detection area.

In at least one embodiment, the load control system may be combined withother types of occupancy or vacancy detectors. In variousimplementations, the system includes a motion detector, a PIR occupancysensor, an ultrasonic occupancy sensor, or any combination thereof.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

The invention will be more fully understood by reference to thefollowing drawings which are for illustrative purposes only:

FIG. 1 is a schematic view of an occupancy sensing load control systemusing a mobile phone detector, according to at least one embodiment ofthe present invention.

FIG. 2 is a schematic view of a ceiling mounted lighting control systemusing a mobile phone detector, according to at least one embodiment ofthe present invention.

FIG. 3 is a schematic flowchart of a light control procedure executed byan occupancy sensing load control system, according to at least oneembodiment of the present invention.

FIG. 4 is a schematic view of a system for controlling electric lightingusing a mobile phone detector and further using a motion detector,according to at least one embodiment of the present invention.

FIG. 5 is a schematic view of a system for controlling electric lightingusing a mobile phone detection, further showing a radio-frequency signalgenerator, according to at least one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Referring more specifically to the drawings, for illustrative purposesthe present invention is embodied in the apparatus generally shown inthe preceding figures. It will be appreciated that the apparatus mayvary as to configuration and as to details of the parts withoutdeparting from the basic concepts as disclosed herein. Furthermore,elements represented in one embodiment as taught herein are applicablewithout limitation to other embodiments taught herein, and incombination with those embodiments and what is known in the art.

The present invention seeks to provide occupancy sensing load controlsystems that can detect the occupancy or vacancy conditionsindependently or in addition to prior-art occupancy detection systemsbased on motion detectors.

According to the present invention, there is provided an occupancysensing load control system that uses radio frequency (RF) signalsemitted by electrically powered, mobile radio-emitting devices such aswireless phones, satellite phones, smart phones, pagers, personaldigital assistants (PDA), tablet computers, wearable personal computers,wireless medical devices, wireless network devices, wireless modems,personal area network devices, wireless cameras, wireless headsets,portable radios, cordless telephones, and global positioning systems(GPS). The invention is particularly directed to detecting personalhand-held communication devices which are energized by an internal orexternal battery and which can be reasonably associated with people whocarry such devices with them in and out from a space. The invention isalso primarily directed to detecting mobile communication devices thatpeople use in their day-to-day life (e.g., cell phones) and that arenormally not associated with occupancy control systems.

It is noted however, that the present invention is not limited todetecting only the personal wearable devices and may be amenable toinclude the detection of mobile communication devices associated withvehicles, such as for example, cell phones, radios and GPS used inmobile fleet communication.

The occupancy sensing load control system comprises an RF signaldetection unit which detects the presence of an RF emitting device in aspace and uses such information to identify the occupancy or vacancycondition and, consequently, to control an electric load in response tothe occupancy or vacancy condition.

Referring to FIG. 1, an embodiment of the occupancy sensing load controlsystem 2 includes a cell phone detector 10, an occupancy/vacancy signalgenerator 12, and a load control circuit 14 which is connected to alighting fixture 20 in a room of a building. Cell phone detector 10 isconfigured to detect the presence of personal RF devices in the room,such RF devices being exemplified by a cell phone 4 in FIG. 1.

It is preferred that detector 10 is designed to detect the presence ofphone 4 within a predetermined distance from the detector and is used tomonitor at least one and/or several of the “transmit” frequency bandsutilized by handheld cellular phones. Particularly, detector 10 shouldbe responsive to a radio frequency signal in the range of at least onetransmit frequency band from the operation of phone 4, (e.g., 824-849MHz and 1850-1910 MHz). By way of example and not limitation, detector10 may be configured to detect cell phones transmitting RF energy usingone or more of the following wireless communication protocols: 2G, 3G,4G, 4G LTE, GSM, GPRS, CDMA, FDMA, TDMA, IDEN, WCDMA, Wifi, WiMAX, andBluetooth.

Detector 10 is not required to monitor or record the phone conversationor determine the identity of the person who may be using the cellularphone and should not normally raise the privacy concerns. Moreover,detector 10 is also not required to detect the usage of phone 4 by itsowner/operator. Its primary function is detecting the mere presence ofphone 4 in a proximity from the detector. It will be appreciated bythose skilled in the art that detector 10 functioning in a “listening”mode will not cause any interference with normal cellular phone serviceor other wireless devices in the monitored area. It will further beappreciated that such passive operation of system 2 will not violatelaws that prohibit monitoring of cellular phone conversations.

It is noted that detector 10 is generally intended to detect a cellularphone signal only within a limited distance from the position of thedetector and reject, ignore or be insensitive to signals originatingfrom greater distances. This may be accomplished, for example, byconfiguring the detection circuit to detect RF signals only if thestrength of such signal is greater than a predetermined threshold. Inone embodiment, such threshold can be made tunable to result indifferent detection distances from the detector 10 to the cell phone 4.Moreover, individual thresholds may be set for different frequencies ordifferent types of the RF signal. This may be particularly usefulconsidering that RF power levels of the transmitted signal may differ,for example, across different types of wireless networks orcommunication protocols.

Cell phone detector 10 may be configured to be responsive to at leastone, more than one, or all of the following operations of cell phone 4resulting in RF transmission: initiating a call, receiving a call,conversation over the cellular network, data transfer, sending and/orreceiving text messages, and registering on the cellular network.

It should be understood that the operation of cell phone detector 10 isnot limited to detecting only the RF signal resulting from the useroperation of phone 4 and may be configured to detect short RFtransmissions of information that phone 4 may be automatically sendingto the cellular network. Such transmissions may be periodic or may occurat varied intervals and may include, for example, phone registrationwith the cellular tower or station, requests for voicemail messages,text messages, or email that may waiting in queue, and the like. Formany cell phones, such transmissions typically occur at intervalsbetween a few minutes and up to 20-30 minutes. Accordingly, as long asphone 4 remains powered up, automatic RF transmissions may reveal thepresence of such phone in a space and may thus be useful for detectingthe occupancy even if phone 4 is in the standby or idle mode.

There are a variety of commercially available cell phone detectors thatcan be utilized by those skilled in the art to practice the presentinvention. One example is Model CSD-710 cell phone detector sold byEnterprise Electronics (http://www.eeontheweb.com). Other examplesinclude PocketHound and Wolfhound cell phone detectors from BerkeleyVaritronics Systems. At least some of such detectors are claimed todetect cell phones during both active phone calls and inactive (standby)modes.

Various types of cell phone detectors that communicate with otherelectronic devices have also been described in the prior art. Forexample, U.S. Pat. No. 8,482,425 describes a cell phone detector forwashing machines. Such detector is attached to the washing machine in alocation that receives RF signals emanated from the interior of thewashing machine. There is also provided a warning device that receives asignal from the detector to generate an alert when the detector hasdetected a RF signal from the interior of the washing machine, whereinthe radio frequency signals have a frequency in a band designated formobile phone signals.

In certain applications, it may be necessary to suppress falsedetections of phones which are outside of the certain area surroundingdetector 10. False detections can be reduced by deploying one or moreadditional RF antennas of the detector within the area and comparing thesignals received by such antennas.

Additionally, detector 10 or one or more of its RF-sensing antennas canbe provided with RF-shielding covers which can block signals arrivingfrom unwanted directions. Each of such covers should be conductive andmay conventionally be made from metal sheet or mesh or various types ofRF absorbing materials. The RF shielding cover may also be cone-shapedin order to provide improved detection in a selected direction. Variousother types of direction-limiting devices may be used to enable detector10 to monitor only the designated space and ignore signals originatingoutside of such space, hereby limiting false triggering.

Referring further to FIG. 1, occupancy/vacancy signal generator 12 isconfigured to receive signals from detector 10 and determine theoccupancy or vacancy condition or status. By way of example and notlimitation, the occupancy condition may be identified by receiving anyindication of qualified RF transmission originating from within the areabeing monitored, while the vacancy condition may be identified by theabsence of such transmission within a predetermined timeout interval.

Load control circuit 14 is connected between an electrical power sourceand the respective electrical load such as lighting fixture 20. Loadcontrol circuit 14 is further configured to receive signals fromoccupancy/vacancy signal generator 12 and control the current suppliedto the electrical load. According to one embodiment, load controlcircuit 14 is configured to turn light off in response to the vacancydetection thus saving electric energy used for lighting. According toone embodiment, load control 14 may further be configured to turn lightson in response to the occupancy detection. Such operation may be enabledby occupancy/vacancy signal generator 12 sending the respectiveoccupancy or vacancy signals to load control circuit 14 and said loadcontrol circuit respectively turning on or off the electric load forlighting fixture 20.

A novel principle behind the detection of the occupancy and/or vacancyin a space is based on the facts that cell phones and other RF-emittinghand-held devices have become very widespread and that such devicestransmit RF signals when in use and even in the idle mode. According tothe survey conducted by Pew Research Center's Internet & American LifeProject, cell phone ownership among adults was 91% in 2012 and that theownership percentage has been steadily increasing since 2004. Anelectronic copy of the report can be found at this internet link:http://pewinternet.org/˜/media//Files/Reports/2012/PIP_Best_Worst_Mobile_113012.pdf). The assessment of the commercial office environmentindicates that cell phone ownership in a typical office is generallyeven greater, often being 100%, which provides a convenient opportunityto determine the occupancy and/or vacancy conditions within office spacewithout relying solely on motion sensors.

The occupancy/vacancy signal generator 12 and load control circuit 14may be combined into an integral load control device which provides thecombined functions of occupancy and/or vacancy determination and controlsignal generation for lighting fixture 20. Alternatively, cell phonedetector 10 may be combined with occupancy/vacancy signal generator 12into a single unit which provides cell phone detection andoccupancy/vacancy signal generation functions.

FIG. 2 schematically shows a portion of an office room 40 where elements10, 12 and 14 of system 2 are mounted on the ceiling in a vicinity oflighting fixture 20. When a room occupant 32 enters room 40 and operateshis hand-held cell phone 4, said cell phone emits RF signal which isdetected by detector 10. In response to such detection, signal generator12 generates an occupancy signal and commands load control circuit 14 toturn on lighting fixture 20. When occupant 32 leaves room 40, signalgenerator 12 generates a vacancy signal after a predetermined timeoutperiod and commands load control circuit 14 to turn off lighting fixture20.

Detector 10 may be configured to detect cell phones only in a proximityof lighting fixture 20 so that room occupants present in other areas ofthe room or outside of the room will not unnecessarily trigger lights onor prevent detection of vacancy condition if there are no occupants nearfixture 20.

Detector 10 may be positioned in a close proximity to lighting fixture20 or even incorporated into the lighting fixture. Since RF signalspropagate through the walls and other obstacles, detector 10 and othercomponents of system 2 may be hidden from the occupants' view andpositioned above the ceiling, behind walls or in an enclosed space. Byadjusting the sensitivity of detector 10, the detection range can be setto include relatively large areas. Accordingly, fewer detectors may beneeded to monitor a given area compared to the case when motiondetectors are used. In one embodiment, cell phone detector 10 may beconfigured to detect mobile phones in multiple rooms of a building or ina large continuous area with multiple partitions.

Multiple detectors 10 may be included into system 2 so as to cover alarger area or reduce false triggering. Any of the elements of system 2may also be incorporated into a wall box switch, into other types ofoccupancy sensors, or into various objects of the building interior.

It may be generally preferred that the occupancy signal is generatedimmediately upon detection of qualified RF transmission within apredetermined area and that the vacancy signal is generated after acertain delay. Such delay may be controlled, for example, by an internaltimer provided with occupancy/vacancy signal generator 12.

Various elements of system 2 may be combined into a single circuit. Forexample, detector 10 and signal generator 12 may be implemented within asingle device while preserving their main functions. Alternatively, atleast some elements of system 2 may be implemented as separate devicesand positioned in different locations. Such components may then beinterconnected using wired or wireless links. For example, it may beadvantageous for some applications to position detector 10 in a vicinityof lighting fixture 20 while incorporating load control circuit 14 intothe wall box switch associated with such lighting fixture.

The flowchart of FIG. 3 illustrates a method of controlling the amountof power delivered from an electrical power source to a lighting loadprovided in a space and shows an exemplary load control process that canbe implemented using the system 2 of FIG. 1, according to one embodimentof the present invention.

Referring to FIG. 3, an occupancy timer is first initialized uponpowering on the occupancy sensing load control system 2 and apredetermined timeout period is set in step 102. By way of example andnot limitation, the timeout period may be set to 10 minutes, 20 minutes,30 minutes, or any other time intervals suited for the particularapplication. Moreover, the occupancy sensing load control system 2 maybe provided with means for controlling the timeout interval by the user.

Referring further to FIG. 3, the output from detector 10 is read in step106. Detector 10 detects a qualified RF signal emitted by a cell phonefrom within the designated space and provides such information in itsoutput signal. Upon reading the “detected” signal from cell phonedetector 10 in step 106 and determining the detection of the phone instep 110, the occupancy/vacancy signal generator 12 sets theoccupancy/vacancy state to “occupied” in step 114 and the occupancytimer is reset in step 118. A control signal is then sent by to thelighting load to turn on the lights in step 122, after which theoperation procedure of system 2 returns to point 104 and the process canrepeat.

Referring yet further to FIG. 3, when no detection occurs, as determinedin step 110, system 2 verifies whether or not the timer is expired instep 140. If the timer is not expired, that is the time elapsed on thetimer is less the predetermined timeout, no signal is sent to thelighting control circuit and the system 2 proceeds back to point 104 forthe next loop.

If the timer is expired at step 140 while no cell phone has beendetected, the vacancy/occupancy state is set to “vacant” in step 144 anda control signal is sent to cease the delivery of power to therespective lighting fixture in step 148, thus turning lights off, afterwhich the system 2 again proceeds back to point 104.

The process illustrated in FIG. 3 can be continued in a loop so that thesystem 2 can detect the occupancy and/or vacancy conditions and controllights accordingly in continuous automatic operation.

In one embodiment, the occupancy sensing load control system 2 may beconfigured to operate in only one of the occupancy sensing or thevacancy sensing modes. It may be useful, for example, when other typesof occupancy sensing systems are employed to detect occupancy or vacancyand the RF-based detection provided by the system 2 of this invention iscomplementary to such other systems.

In one embodiment, which is schematically illustrated in FIG. 4, system2 may further include a motion detector 26. The occupancy/vacancy signalgenerator 12 may then be configured to receive input from both of thecell phone detector 10 and the motion detector 26 and use variousalgorithms and criteria to determine the occupancy or vacancy conditionsin the room.

In a non-limiting example, the occupancy condition may be triggered wheneither one of detectors 10 and 26 detects a valid signal while thevacancy condition may be triggered when no signal is detected by bothdetectors after a predetermined timeout. In various embodiment of thepresent invention, signal generator 12 may employ separate processloops, process logic, criteria, timers and timeout intervals fordetectors 10 and 26. Furthermore, system 2 may incorporate additionaldetectors of either type and may also include occupancy detectors ofother types known in the art.

In one embodiment of the present invention, system 2 may further includemeans for producing an audible or visible alarm. For example, such alarmmay be used to provide occupancy sensing feedback to building occupantsor to perform system testing or tune up.

FIG. 5 shows an embodiment which further includes an active RF signalgenerator 28. RF signal generator 28 is configured to emit RF signalstriggering an RF response from phone 4 so that such response can bedetected by cell phone detector 10. Accordingly, system 2 can “poll”wireless devices that may be present in the room and determine theoccupancy status at the time of polling.

The inclusion of RF signal generator 28 into system 2 may be useful, forexample, for reducing the uncertainty of cell phone detection in thecase when one or more cell phones are present in the monitored space andall of such phones are in a standby mode. Since timing of RF emissionsby cell phones in standby is unpredictable, forceful triggering of phoneresponses may improve the detection rate and possible reduce theoccurrence of false vacancy detection.

It will be appreciate by those skilled in the art that most cell phonescontinue receiving signals from base stations even when in a standby oridle state, as a matter of the cellular protocol operation.Conventionally, when a cell phone is in a stationary location at anypoint of time, it will receive a stronger signal from one base stationwhich is closest to the phone location. As the signal from another basestation becomes stronger than that from the previous station, the cellphone initiates a process of registering with the new base station. Suchregistration process involves sending one or more RF signals which canbe detected by cell phone detector 10 thus triggering the occupancycondition.

In one embodiment, RF signal generator 28 is configured to generate andemit a pseudo base station signal corresponding to a base station signalfor phone 4. An exemplary device and process of detectingtelephone-activated devices in idle state using the generation andemission a pseudo base station signal corresponding to a base stationsignal for a cellular phone are described, for example, in U.S. Pat. No.47,162,285.

RF signal generator 28 may be configured as a standalone deviceoperating independently from the other elements of system 2. Forexample, it can be configured to periodically send response-triggeringsignals at predefined time intervals. Alternatively, RF signal generator28 may be controlled by or be in a communication to theoccupancy/vacancy signal generator 12 using a wired or wireless link 44.In such a case, the suitable times of RF transmissions by RF signalgenerator 28 may be determined by occupancy/vacancy signal generator 12.

It is noted that useful implementations of system 2 are not limited todetecting the occupancy or vacancy condition based on RF emission ofcell phones and may be applied to the case when other types of personalRF-emitting communication devices may be used for such detection.Particularly, detector 10 may be configured to detect non-cellularmobile phones, satellite phones, smart phones, pagers, personal digitalassistants (PDA), tablet computers, mobile personal computers, wirelessmedical devices, wireless network devices, wireless modems, personalarea network devices, wireless cameras, wireless headsets, portableradios, cordless telephones, and global positioning systems (GPS).

Further embodiments and implementations of system 2 may include signaldiscrimination so as to detect only certain types of wirelesscommunication devices while ignoring other types of RF-emitting devices.For example, ignoring signals that are typical for stationary devicessuch as wireless routers, radio-frequency identification devices (RFIDs)or systems, wireless phone base stations, and the like, may beadvantageous for reducing false occupancy detections.

System 2 may also be provided with a memory and a memory processing unit(not shown) to store the RF signatures of individual devices detected bydetector 10. Each newly detected signal may then be compared to theindividual signatures stored in the memory and a predefined logic can beused to determine the occupancy status based on various criteria. Thecriteria used to determine the occupancy and/or vacancy conditions mayalso include analyzing the time of the day, the frequency of occupancyor vacancy triggering, the prevailing types of RF signals in a space andother factors.

For example, system 2 may be configured to ignore devices that operate24 hours a day or the number of hours beyond a certain thresholdsignificantly exceeding the expected work day, since such devices aremuch more likely to be stationary and not associated with the presenceor absence of a building room occupant. The signal processing circuitryof system 2 may be implemented with learning algorithms so that suchsystem can automatically identify and separate stationary devices fromthose associated with building occupants. Alternatively, or in additionto this, system 2 may be provided with user-operable controls orswitches allowing the system to memorize devices that should be includedin the detection and/or the devices that should be ignored.

For example, system 2 may be provided with a user-accessible button orswitch which triggers the detection and storage of RF signatures ofradio-emitting devices that should be ignored in its memory. Such buttonor switch may be activated at night when no people typically occupyingthe space during the day time are present. As the signals from thedevices to be ignored are captured and stored, system 2 will preventtriggering an occupancy condition when new signals are detected fromsuch devices.

In an alternative to button or switch activated detection of the RFdevices to be ignored, system 2 may also be provided with a wirelesssignal receiver so that such detection can be triggered by the userremotely using a remote control unit or through wired or wirelessnetwork.

It is noted that the present invention 2 is not limited to controllingelectric lighting fixtures and may also be applied to the case ofcontrolling other types of electric loads in response to the detectedvacancy and/or occupancy conditions, such as, for example, heatingunits, air conditioning units, ventilation units, or security systems.In one embodiment, system 2 may be configured to arm an alarm systemwhen a vacancy condition for a prolonged time period is detected.

Further details of operation of system 2 shown in the drawing figures aswell as its possible variations will be apparent from the foregoingdescription of preferred embodiments. Although the description abovecontains many details, these should not be construed as limiting thescope of the invention but as merely providing illustrations of some ofthe presently preferred embodiments of this invention. Therefore, itwill be appreciated that the scope of the present invention fullyencompasses other embodiments which may become obvious to those skilledin the art, and that the scope of the present invention is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.” Allstructural, chemical, and functional equivalents to the elements of theabove-described preferred embodiment that are known to those of ordinaryskill in the art are expressly incorporated herein by reference and areintended to be encompassed by the present claims. Moreover, it is notnecessary for a device or method to address each and every problemsought to be solved by the present invention, for it to be encompassedby the present claims. Furthermore, no element, component, or methodstep in the present disclosure is intended to be dedicated to the publicregardless of whether the element, component, or method step isexplicitly recited in the claims. No claim element herein is to beconstrued under the provisions of 35 U.S.C. 112, sixth paragraph, unlessthe element is expressly recited using the phrase “means for.”

What is claimed is:
 1. An occupancy sensing load control systemcomprising: a signal-generating unit configured for periodicallygenerating a radio control signal at predefined time intervals, saidradio control signal being configured to trigger a response signal froma mobile radio-emitting communication device located within apredetermined distance from said signal-generating unit; aradio-frequency detector configured to detect said response signal; anoccupancy/vacancy signal generating device configured to determineoccupancy and/or vacancy condition in response to the result of adetection of said response signal; and a load control device connectedbetween an electrical power source and an electrical load and configuredto control the current supplied to said electrical load in response to asignal generated by said occupancy/vacancy signal generating device. 2.The system as recited in claim 1, further comprising an internalresettable timer, wherein said occupancy/vacancy signal generatingdevice is configured for generating a vacancy condition in response toan absence of a qualified radio-frequency response signal within apredetermined timeout period.
 3. The system as recited in claim 1,further comprising a memory unit configured to store signalidentification information from previously detected radio-emittingcommunication devices, and a memory processing unit configured forcomparing said signal to the signal identification information stored insaid memory unit, wherein said occupancy/vacancy signal generatingdevice is configured to ignore the detection of at least some responsesignals which signal identification information is stored in said memoryunit.
 4. The system as recited in claim 1, further comprising a motiondetector, wherein the occupancy/vacancy signal generating device isconfigured to determine occupancy and/or vacancy condition based on theinput from both said radio-frequency detector and said motion detector.5. The system as recited in claim 4, wherein said motion detectorcomprises a PIR sensor.
 6. The system as recited in claim 4, whereinsaid motion detector comprises an ultrasonic sensor.
 7. The system asrecited in claim 1, wherein the mobile radio-emitting communicationdevice is a personal hand-held communication device energized by aninternal or external battery.
 8. The system as recited in claim 1,wherein the mobile radio-emitting communication device is a cell phone.9. The system as recited in claim 1, wherein the radio-frequencydetector is configured to simultaneously monitor more than one radiofrequency band.
 10. The system as recited in claim 1, wherein theoccupancy/vacancy signal generating device is configured to determineoccupancy condition only when said response signal has a strength thatis greater than a predetermined threshold.
 11. The system as recited inclaim 10, wherein said threshold is adjustable by a user.
 12. The systemas recited in claim 1, wherein the radio-frequency detector comprisestwo or more antennas and configured to compare signals received by saidantennas.
 13. The system as recited in claim 1, wherein said electricalload comprises a lighting fixture.
 14. The system as recited in claim 1,wherein said electrical load comprises an air conditioning orventilation unit.
 15. The system as recited in claim 1, wherein saidelectrical load comprises a heating unit.
 16. The system as recited inclaim 1, wherein said electrical load comprises a security system. 17.The system as recited in claim 1, wherein said load control device isconfigured to arm an alarm system when a vacancy condition for apredefined time period is detected.
 18. The system as recited in claim1, wherein said radio-frequency detector is provided with a radiofrequency shielding structure configured for blocking signals arrivingfrom predetermined unwanted directions.
 19. The system as recited inclaim 1, wherein said radio-frequency detector is provided with adirection-limiting device and configured to detect signals only in adesignated space and ignore signals originating outside of saiddesignated space.
 20. A method of controlling the amount of powerdelivered from an electrical power source to an electrical load providedin a space, said method comprising the steps of: providing aradio-frequency sensor in said space; providing a radio-frequencysignal-generating unit; periodically transmitting a radio-frequencycontrol signal into said space at predefined time intervals, saidradio-frequency control signal being capable of triggering a responsefrom a mobile radio frequency communication device located within saidspace; changing the amount of power delivered to the electrical load inresponse to the absence of a qualified radio-frequency response signalduring a predetermined period of time.